Make prober more generic

pkg/activator/handler/handler.go

@@ -90,7 +90,7 @@ func New(l *zap.SugaredLogger, r activator.StatsReporter, t *activator.Throttler
 	}
 }
 
-func withOrigProto(or *http.Request) prober.ProbeOption {
+func withOrigProto(or *http.Request) prober.Preparer {
 	return func(r *http.Request) *http.Request {
 		r.Proto = or.Proto
 		r.ProtoMajor = or.ProtoMajor
@@ -113,7 +113,13 @@ func (a *activationHandler) probeEndpoint(logger *zap.SugaredLogger, r *http.Req
 
 	err := wait.PollImmediate(100*time.Millisecond, a.probeTimeout, func() (bool, error) {
 		attempts++
-		ret, err := prober.Do(reqCtx, a.probeTransportFactory(), target.String(), queue.Name, withOrigProto(r))
+		ret, err := prober.Do(
+			reqCtx,
+			a.probeTransportFactory(),
+			target.String(),
+			prober.WithHeader(network.ProbeHeaderName, queue.Name),
+			prober.ExpectsBody(queue.Name),
+			withOrigProto(r))
 		if err != nil {
 			logger.Warnw("Pod probe failed", zap.Error(err))
 			return false, nil

pkg/network/prober/prober.go

@@ -26,29 +26,45 @@ import (
 	"github.com/pkg/errors"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/wait"
-
-	"github.com/knative/serving/pkg/network"
 )
 
 // TransportFactory is a function which returns an HTTP transport.
 type TransportFactory func() http.RoundTripper
 
-// ProbeOption is a way for caller to modify the HTTP request before it goes out.
-type ProbeOption func(r *http.Request) *http.Request
+// Preparer is a way for the caller to modify the HTTP request before it goes out.
+type Preparer func(r *http.Request) *http.Request
+
+// Verifier is a way for the caller to validate the HTTP response after it comes back.
+type Verifier func(r *http.Response, b []byte) (bool, error)
+
+// WithHeader sets a header in the probe request.
+func WithHeader(name, value string) Preparer {
+	return func(r *http.Request) *http.Request {
+		r.Header.Set(name, value)
+		return r
+	}
+}
+
+// ExpectsBody validates that the body of the probe response matches the provided string.
+func ExpectsBody(body string) Verifier {
+	return func(r *http.Response, b []byte) (bool, error) {
+		return string(b) == body, nil
+	}
+}
 
 // Do sends a single probe to given target, e.g. `http://revision.default.svc.cluster.local:81`.
-// headerValue is the value for the `k-network-probe` header.
 // Do returns whether the probe was successful or not, or there was an error probing.
-func Do(ctx context.Context, transport http.RoundTripper, target, headerValue string, pos ...ProbeOption) (bool, error) {
+func Do(ctx context.Context, transport http.RoundTripper, target string, ops ...interface{}) (bool, error) {
 	req, err := http.NewRequest(http.MethodGet, target, nil)
 	if err != nil {
 		return false, errors.Wrapf(err, "%s is not a valid URL", target)
 	}
-	for _, po := range pos {
-		req = po(req)
+	for _, op := range ops {
+		if po, ok := op.(Preparer); ok {
+			req = po(req)
+		}
 	}
 
-	req.Header.Set(network.ProbeHeaderName, headerValue)
 	req = req.WithContext(ctx)
 	resp, err := transport.RoundTrip(req)
 	if err != nil {
@@ -59,7 +75,16 @@ func Do(ctx context.Context, transport http.RoundTripper, target, headerValue st
 	if err != nil {
 		return false, errors.Wrap(err, "error reading body")
 	}
-	return resp.StatusCode == http.StatusOK && string(body) == headerValue, nil
+
+	for _, op := range ops {
+		if vo, ok := op.(Verifier); ok {
+			ok, err := vo(resp, body)
+			if err != nil || !ok {
+				return false, err
+			}
+		}
+	}
+	return resp.StatusCode == http.StatusOK, nil
 }
 
 // Done is a callback that is executed when the async probe has finished.
@@ -101,19 +126,19 @@ func New(cb Done, transportFactory TransportFactory) *Manager {
 // Otherwise Offer starts a goroutine that periodically executes
 // `Do`, until timeout is reached, the probe succeeds, or fails with an error.
 // In the end the callback is invoked with the provided `arg` and probing results.
-func (m *Manager) Offer(ctx context.Context, target, headerValue string, arg interface{}, period, timeout time.Duration) bool {
+func (m *Manager) Offer(ctx context.Context, target string, arg interface{}, period, timeout time.Duration, ops ...interface{}) bool {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	if m.keys.Has(target) {
 		return false
 	}
 	m.keys.Insert(target)
-	m.doAsync(ctx, m.transportFactory, target, headerValue, arg, period, timeout)
+	m.doAsync(ctx, m.transportFactory, target, arg, period, timeout, ops...)
 	return true
 }
 
 // doAsync starts a go routine that probes the target with given period.
-func (m *Manager) doAsync(ctx context.Context, transportFactory TransportFactory, target, headerValue string, arg interface{}, period, timeout time.Duration) {
+func (m *Manager) doAsync(ctx context.Context, transportFactory TransportFactory, target string, arg interface{}, period, timeout time.Duration, ops ...interface{}) {
 	go func() {
 		defer func() {
 			m.mu.Lock()
@@ -124,8 +149,9 @@ func (m *Manager) doAsync(ctx context.Context, transportFactory TransportFactory
 			result bool
 			err    error
 		)
+
 		err = wait.PollImmediate(period, timeout, func() (bool, error) {
-			result, err = Do(ctx, transportFactory(), target, headerValue)
+			result, err = Do(ctx, transportFactory(), target, ops...)
 			return result, err
 		})
 		m.cb(arg, result, err)

pkg/network/prober/prober_test.go

@@ -70,7 +70,7 @@ func TestDoServing(t *testing.T) {
 	}}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			got, err := Do(context.Background(), network.NewAutoTransport(), ts.URL, test.headerValue)
+			got, err := Do(context.Background(), network.NewAutoTransport(), ts.URL, WithHeader(network.ProbeHeaderName, test.headerValue), ExpectsBody(test.headerValue))
 			if want := test.want; got != want {
 				t.Errorf("Got = %v, want: %v", got, want)
 			}
@@ -82,7 +82,7 @@ func TestDoServing(t *testing.T) {
 }
 
 func TestBlackHole(t *testing.T) {
-	got, err := Do(context.Background(), network.NewAutoTransport(), "http://gone.fishing.svc.custer.local:8080", systemName)
+	got, err := Do(context.Background(), network.NewAutoTransport(), "http://gone.fishing.svc.custer.local:8080")
 	if want := false; got != want {
 		t.Errorf("Got = %v, want: %v", got, want)
 	}
@@ -92,7 +92,7 @@ func TestBlackHole(t *testing.T) {
 }
 
 func TestBadURL(t *testing.T) {
-	_, err := Do(context.Background(), network.NewAutoTransport(), ":foo", systemName)
+	_, err := Do(context.Background(), network.NewAutoTransport(), ":foo")
 	if err == nil {
 		t.Error("Do did not return an error")
 	}
@@ -150,7 +150,7 @@ func TestDoAsync(t *testing.T) {
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			m := New(test.cb, network.NewAutoTransport)
-			m.Offer(context.Background(), ts.URL, test.headerValue, test.name, 50*time.Millisecond, 2*time.Second)
+			m.Offer(context.Background(), ts.URL, test.name, 50*time.Millisecond, 2*time.Second, WithHeader(network.ProbeHeaderName, test.headerValue), ExpectsBody(test.headerValue))
 			<-wch
 		})
 	}
@@ -187,7 +187,7 @@ func TestDoAsyncRepeat(t *testing.T) {
 		wch <- arg
 	}
 	m := New(cb, network.NewAutoTransport)
-	m.Offer(context.Background(), ts.URL, systemName, 42, 50*time.Millisecond, 3*time.Second)
+	m.Offer(context.Background(), ts.URL, 42, 50*time.Millisecond, 3*time.Second, WithHeader(network.ProbeHeaderName, systemName), ExpectsBody(systemName))
 	<-wch
 	if got, want := c.calls, 3; got != want {
 		t.Errorf("Probe invocation count = %d, want: %d", got, want)
@@ -210,7 +210,7 @@ func TestDoAsyncTimeout(t *testing.T) {
 		wch <- arg
 	}
 	m := New(cb, network.NewAutoTransport)
-	m.Offer(context.Background(), ts.URL, systemName, 2009, 10*time.Millisecond, 200*time.Millisecond)
+	m.Offer(context.Background(), ts.URL, 2009, 10*time.Millisecond, 200*time.Millisecond)
 	<-wch
 }
 
@@ -225,10 +225,10 @@ func TestAsyncMultiple(t *testing.T) {
 		wch <- 2006
 	}
 	m := New(cb, network.NewAutoTransport)
-	if !m.Offer(context.Background(), ts.URL, systemName, 1984, 100*time.Millisecond, 1*time.Second) {
+	if !m.Offer(context.Background(), ts.URL, 1984, 100*time.Millisecond, 1*time.Second) {
 		t.Error("First call to offer returned false")
 	}
-	if m.Offer(context.Background(), ts.URL, systemName, 1982, 100*time.Millisecond, 1*time.Second) {
+	if m.Offer(context.Background(), ts.URL, 1982, 100*time.Millisecond, 1*time.Second) {
 		t.Error("Second call to offer returned true")
 	}
 	if got, want := m.len(), 1; got != want {

pkg/reconciler/autoscaling/kpa/scaler.go

@@ -53,9 +53,14 @@ const (
 	reenqeuePeriod = 1 * time.Second
 )
 
+var probeOptions = []interface{} {
+	prober.WithHeader(network.ProbeHeaderName, activator.Name),
+	prober.ExpectsBody(activator.Name),
+}
+
 // for mocking in tests
 type asyncProber interface {
-	Offer(context.Context, string, string, interface{}, time.Duration, time.Duration) bool
+	Offer(context.Context, string, interface{}, time.Duration, time.Duration, ...interface{}) bool
 }
 
 // scaler scales the target of a kpa-class PA up or down including scaling to zero.
@@ -112,7 +117,7 @@ func activatorProbe(pa *pav1alpha1.PodAutoscaler, transport http.RoundTripper) (
 	if pa.Status.ServiceName == "" {
 		return false, nil
 	}
-	return prober.Do(context.Background(), transport, paToProbeTarget(pa), activator.Name)
+	return prober.Do(context.Background(), transport, paToProbeTarget(pa), probeOptions...)
 }
 
 // pre: 0 <= min <= max && 0 <= x
@@ -172,7 +177,7 @@ func (ks *scaler) handleScaleToZero(pa *pav1alpha1.PodAutoscaler, desiredScale i
 
 		// Otherwise (any prober failure) start the async probe.
 		ks.logger.Infof("%s is not yet backed by activator, cannot scale to zero", pa.Name)
-		if !ks.probeManager.Offer(context.Background(), paToProbeTarget(pa), activator.Name, pa, probePeriod, probeTimeout) {
+		if !ks.probeManager.Offer(context.Background(), paToProbeTarget(pa), pa, probePeriod, probeTimeout, probeOptions...) {
 			ks.logger.Infof("Probe for %s is already in flight", pa.Name)
 		}
 		return desiredScale, false

pkg/reconciler/autoscaling/kpa/scaler_test.go

@@ -583,7 +583,7 @@ type countingProber struct {
 	count int
 }
 
-func (c *countingProber) Offer(ctx context.Context, target, headerValue string, arg interface{}, period, timeout time.Duration) bool {
+func (c *countingProber) Offer(ctx context.Context, target string, arg interface{}, period, timeout time.Duration, ops ...interface{}) bool {
 	c.count++
 	return true
 }